Crop a 16:9 master to 1:1 and 4:5: widths 0.5625 and 0.45

To crop a 16:9 video to a centred 1:1, send a Sume video-filter crop op with x 0.21875, y 0, width 0.5625 and height 1. For a centred 4:5 use x 0.275, y 0, width 0.45 and height 1. LinkedIn's video ad specs list both 1:1 and 4:5 among four supported ratios.

The ratio list is from LinkedIn's page (read 2026-10-10). The fractions are arithmetic from the Video filter docs, which define crop as fractions of the source frame.

What LinkedIn lists

LinkedIn's video ad specs list the aspect ratios 4:5 (vertical, 0.8), 9:16 (vertical, 0.57), 16:9 (landscape, 1.78) and 1:1 (square, 1.0). They list a minimum and maximum width of 360 and 1920 pixels, a minimum and maximum height of 360 and 1920 pixels, a file size of 75 KB to 500 MB, a duration of 3 seconds to 30 minutes, MP4 files, and a recommended 30 frames per second.

The crop arithmetic

A frame with width W and height H has ratio W/H. A 16:9 frame is 1.7778. To keep the full height and crop the width to a target ratio r, the kept width fraction is r divided by 1.7778. For 1:1 that is 0.5625, so the crop starts at (1 - 0.5625) / 2 = 0.21875. For 4:5, r is 0.8, so the fraction is 0.45 and the start is 0.275. For 9:16, r is 0.5625, so the fraction is 0.3164 and the start is 0.3418.

Sending the crop

The Video filter docs say crop takes x and y in 0 to 1, width and height in 0.05 to 1, with x plus width and y plus height no more than 1. The compiler rounds to even values for yuv420p. On a 1920 x 1080 source the 1:1 fractions come out at exactly 1080 pixels wide, and the 4:5 fractions at exactly 864, both even. The 9:16 fractions give about 607.5 pixels, so rounding applies and the ratio is not exact to the pixel.

Check first: POST /v1/video-filter/check is unbilled and returns diagnostics instead of a 400. The encode itself is $0.02 per job, with a source limit of 300 seconds. For longer sources, trim first or render in parts.

• Import the clip to media.sume.com first.
• Run the free check call.
• Send the encode with an Idempotency-Key and read the new video_url.

Then what

The crop is geometry only; it does not scale. If LinkedIn needs at least 360 pixels on each edge, a 1080 x 1080 or 864 x 1080 crop passes by a wide margin. The page's maximum is 1920 per edge, and both crops are under it. If you want a different frame size, put the cropped MP4 into Timeline 1.0 with cover fit and set output width and height, which accept even values from 256 to 2160.

The same arithmetic extends to any centred crop. Pick the ratio, divide it by the source ratio, keep the result as the width fraction if the target is narrower than the source, and centre it.

Centring is a choice, not a rule. If the speaker stands left of centre in the 16:9 frame, shift x so the face stays inside the kept window, remembering that x plus width must not pass 1. For the 1:1 crop the largest legal x is 0.4375, and for 4:5 it is 0.55. Anything beyond those values is refused as video_filter_crop_out_of_bounds.

Doing the two crops from the same master keeps the story consistent across placements. The 16:9 original stays on media.sume.com untouched, because a crop returns a new MP4 and never changes the source, so you can derive the square and the 4:5 versions separately and compare them before choosing which one to run.